The invention relates to a process and circuit for heating a glow plug of a given glow plug type in a given arrangement in an internal combustion engine to a predetermined temperature.
Glow plugs are used for example in diesel engines for igniting the fuel during starting or also for ion current acquisition in the combustion chamber of a diesel engine.
So that one such glow plug can perform its function, in a heat-up phase it must be heated to a certain temperature.
Glow plugs are known which have self-regulating heat-up characteristics. They are connected time-controlled to a power supply voltage and as a result of their self-regulating behavior they are heated up to a certain temperature.
Electronic control of the heat-up of the glow plug is also known. In this case the electrical power supply to the glow plug is controlled via an electronic control circuit such that the stipulated determined temperature is reached as quickly as possible and is not exceeded.
The known processes of self-regulation and electronic control however fail when the glow plug is to be heated very quickly to a high temperature, for example in two seconds to 1000xc2x0 C. In electronic control for example this is due to the fact that as a result of the high dynamics of the heat-up process, with consideration of the manufacturing tolerances, major problems arise since under all circumstances overheating of the glow plug, even if only brief, must be avoided.
The object of the invention is therefore to devise a process and a circuit for heating up a glow plug with which heat-up to a relatively high temperature within a very short time interval can be achieved.
This object is achieved in the process of the invention where the heat energy needed for heat-up to a predetermined temperature is determined from the parameters of the respective glow plug type in a given arrangement and from the initial temperature of the glow plug, and the heat energy is supplied to the glow plug within a selected heat-up time interval.
One preferred embodiment of the process comprises heating up a glow plug of in an internal combustion engine to a predetermined temperature within a chosen heat-up time interval using the glow plug type and initial temperature of the glow plug to determine the heat energy needed.
A circuit for heating up the glow plug in an internal combustion engine comprises a power supply voltage across the glow plug in a series circuit with a switch, a measurement resistor, and an electronic control and evacuation unit. The required heat energy is supplied to the glow plug within a chosen heat-up time interval.
Using the pertinent drawings one especially preferred embodiment of the invention is described below.